RENTON – Earl Thomas is attempting to reinvent the way he plays safety.

Thomas, a Pro Bowl free safety, has been called aggressive, explosive, fearless, competitive and a ball hawk. Now, in his fourth season, he’s trying to add a new layer, although slapping a one-word label on what he’s doing is more difficult.

“I’m challenging quarterbacks more as far as redefining how you can come up and play almost as a linebacker but still be playing middle field,” Thomas said.

Thomas is Seattle’s firefighter, a safety who eliminates big plays because of his presence deep in Seattle’s secondary. But through the years he thought doing so also exposed a soft underbelly in the middle.

So this year, with a cornerback unit led by Richard Sherman and Brandon Browner (when healthy), Thomas decided to play closer to the line of scrimmage.

“It’s about being real aggressive in the middle instead of baby-sitting the corners,” Thomas said. “Why should you baby-sit corners when you have good corners like that? My first three years, I left a lot of plays out there in the middle just because I was so worried about getting over there for Sherm or BB. But now that’s not the case.”

There’s no way Thomas could play closer to the line if he didn’t trust his corners. Sherman, Browner and Walter Thurmond have shown they can hold their own against receivers outside.

In Sunday’s win over San Francisco, for example, Sherman lined up against hulking tight end Vernon Davis. He tracked Davis down the sideline, then beat him in the air for a jump-ball interception.

That trust gives Thomas the freedom to focus on the middle of the field instead of paying so much attention outside.

He’s still responsible for controlling and eliminating big plays, which the Seahawks have done. Seattle ranks first in the league in passing yards allowed (113 per game), and it’s not really close. The longest pass play against Seattle in the first two games went for 27 yards.

“I would just love to play with the corners they have in Seattle,” said NFL Network analyst Darren Sharper, a five-time Pro Bowl safety. “A safety who has great recognition skills and great instincts, like Earl has, if they throw the ball in the middle of the field, he should be right there anticipating where they’re going now. Those corners pretty much take away two-thirds of the field.

“He should lick his chops and start playing games with offenses daring them to throw the ball over the middle.”

The change in Thomas’ positioning is noticeable, although it doesn’t exactly jump out. It’s a few steps here or there, but those few steps can be the difference in getting to a crossing route over the middle.

“If you’re looking at the TV copy of the game,” Thomas said, “you can probably always see me in the frame now.”

And last year?

“You’d never see me.”

Thomas can play that way for two reasons. First, he’s one of Seattle’s fastest players, and he thinks his speed can get him to where he needs to go. The other reason? He thinks seam routes — the ones he’s most responsible for eliminating, deep down the middle of the field — are thrown in a way that allows him to still defend them.

“I’m always going to be around the ball,” Thomas said. “I can get in the running game and also take away the seams. When you look at how quarterbacks in this league throw seams, it’s not up in the air, it’s always on the dart. And I think I have the speed to get there.”

In the first quarter against Carolina, quarterback Cam Newton fired a pass to tight end Greg Olsen in the seam. It looked like Olsen was going to make the catch, but Thomas came flying in and jarred the ball loose. The Panthers punted.

“That’s because he was playing closer,” Sherman said of Thomas. “You can’t fit those little passes in there.”

Said Thomas, “Cam tried me a couple times, and it didn’t work out.”

Thomas’ positioning also allows him to be more involved in stopping the run. He pointed to one read-option play against San Francisco in which he stopped quarterback Colin Kaepernick for a modest gain. A year ago, Thomas said, that might have gone for a big play.

“Shoot, as you can see, the more the NFL has gotten pass-friendly, the more safeties back off,” Sherman said. “But he’s challenging himself. That’s a great asset for our team.”